MDCV: a decentralized and collusion-resistant consistency verification scheme for multi-cloud storage

Abstract Ensuring data consistency across multiple cloud service providers (CSPs) is essential for maintaining the reliability and security of multi-cloud storage systems. However, most existing related works rely on trusted third parties (TTPs) and are vulnerable to collusion, which undermines trust and efficiency. To overcome these challenges, we propose MDCV, a decentralized and collusion-resistant consistency verification scheme for multi-cloud storage. MDCV leverages smart contracts to autonomously coordinate consistency verification process without relying on any TTP, thereby ensuring transparency, immutability, and trust-free verification. Specifically, MDCV employs a collusion-resistant public verification protocol in which each CSP binds the proof generation process to its private key and generates non-interactive, publicly verifiable consistency proof using pseudo-random challenges derived from blockchain transaction IDs. This design not only prevents colluding CSPs from generating forged proofs but also supports public auditing. Formal security analysis demonstrates the soundness of the proposed scheme, while experimental results show that MDCV achieves efficient proof generation and verification with lower computational and communication overhead, validating its practicality in real-world multi-cloud backup auditing systems.